The present invention relates to an apparatus for estimating the lifetime of a surge protective device (SPD) using the discharge characteristics of a metal oxide varistor (MOV), which can check the damage state of the MOV by applying an impulse voltage to the MOV and checking the discharge current of the MOV.
With the recent development of the data communication technology, electronic devices directly connected to an external communication line for transmitting/receiving data have suddenly increased. Accordingly, there is a great need for an overvoltage protective device for preventing the failure of an electronic device attributable to the influence of surge flowing into the electronic device.
A known overvoltage protective device includes an SPD for preventing an overvoltage from being applied to an electronic device due to surge. The SPD includes various elements, such as an MOV. The SPD is gradually damaged when an overvoltage, such as surge, continues to flow into the SPD, and stops operating at a specific point of time. Accordingly, an external electronic device connected to the SPD cannot be normally protected, and an electronic device may be directly damaged by a transient voltage/current.
That is, when a surge voltage of a protection capacity or more is input to the SPD, elements are frequently damaged and shorted. Accordingly, although the lifespan of the SPD has expired, the replace time of the SPD is missed because whether the SPD has been damaged cannot be checked with the naked eye, thereby damaging equipment.
In Korean Patent No. 10-1253229, the short circuit of an MOV is detected and an SPD indicates the short circuit using an LED. However, the conventional technology has a problem in that equipment is damaged when surge is received because whether the SPD has failed cannot be checked if the SPD is not shorted, but is partially damaged.
Furthermore, in Korean Patent No. 10-1303202, received energy is checked based on the amount and number of surge currents, and a failure rate of an SPD is estimated. However, the conventional technology has problems in that an error rate of input surge current measurement becomes an important factor and an excellent CT must be provided for the error rate.